(1. 中國航發(fā)北京航空材料研究院 先進(jìn)鈦合金航空科技重點(diǎn)實(shí)驗(yàn)室，北京 100095；
2. 中國鋼研科技集團(tuán)有限公司 鋼研納克檢測技術(shù)股份有限公司，北京 100081)
摘 要: Ti6242等一些近α 和α+β 型鈦合金存在保載疲勞行為，研究結(jié)果顯示其保載疲勞失效內(nèi)在機(jī)制主要與周期載荷作用下材料內(nèi)部微區(qū)不均勻變形行為密切相關(guān)。本研究在對鈦合金保載疲勞現(xiàn)有軟-硬取向模型的理解基礎(chǔ)上，通過設(shè)計(jì)Ti6242合金在不同保載時間和應(yīng)力比載荷作用下的保載疲勞試驗(yàn)，驗(yàn)證保載時間和應(yīng)力比對保載疲勞壽命影響規(guī)律，更長的保載時間引起Ti6242合金保載疲勞壽命單調(diào)衰減并趨于穩(wěn)定，更高的應(yīng)力比則引起其保載疲勞壽命呈指數(shù)增長。從應(yīng)力-應(yīng)變曲線分析角度表征Ti6242合金在保載疲勞載荷下的應(yīng)力、應(yīng)變響應(yīng)特征，分析顯示保載時間主要影響材料內(nèi)部局部應(yīng)力、應(yīng)變的重新分布和累積變形協(xié)調(diào)過程，應(yīng)力比則主要加劇材料在循環(huán)載荷中內(nèi)部軟相和硬相的微區(qū)應(yīng)變差別。
關(guān)鍵字: 鈦合金；保載時間；應(yīng)力比；保載疲勞；應(yīng)力；應(yīng)變
（1. Aviation Key Laboratory of Science and Technology on Advanced Titanium Alloys, AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China;
2. NCS Testing Technology Co., Ltd., China Iron and Steel Research Institute Group, Beijing 100081, China）
Abstract:These near α and α+β titanium alloys, such as Ti6242 alloy, usually exhibit dwell fatigue failure characteristic. The investigation results show that the dwell fatigue failure internal mechanism of these titanium alloy is mainly related to the inhomogeneous plastic deformation and local stress concentration under the dwell fatigue load. In this study, the dwell fatigue tests with different dwell time and stress ratio were designed to verify their influences on dwell fatigue life based on the understanding of the soft-hard orientation models. It is found that the dwell fatigue life of Ti6242 titanium alloy decreases monotonously with the increase of dwell time and tends to stabilize, but increases exponentially with stress ratio. According to the detailed analysis of stress and strain curves of Ti6242 alloy under dwell fatigue load, the dwell time mainly affects the redistribution and accumulative coordination processes of local stress and strain, while the stress ratio can intensify the local strain difference between the soft phase and the hard phase in the material.
Key words: titanium alloy; dwell time; stress ratio; dwell fatigue; stress; strain
